JP3255586B2 - Electrode plate for plasma etching - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode plate used for plasma etching a thin film such as a silicon oxide film formed on a wafer or a wafer surface in a semiconductor device manufacturing process. The present invention relates to a plasma etching electrode plate made of a glassy carbon plate that can be used stably for a long period of time while obtaining a uniform etching rate in the processing of a large-sized wafer and reducing the consumption of the electrode surface by plasma.

In a plasma etching process, a reactive gas (CF ₄ , A
(r, O ₂ etc.) by applying high frequency power between the electrodes while discharging, and etching the photoresist part using the generated gas plasma to form a fine circuit pattern with high precision Done. The planar electrode used for this plasma etching process needs to have not only excellent conductivity, but also high purity that does not contaminate the wafer and chemical stability that is not easily etched, and currently satisfy these material requirements. For example, an electrode plate formed of a glassy carbon material has been useful.

A glassy carbon material is a macroscopically nonporous hard carbon material obtained by carbonizing a thermosetting resin, and has high strength, low chemical reactivity, gas impermeability, self-lubricating property, and robustness. It has characteristics such as low impurity content and the like, but there is an advantage in that fine particles which cause contamination of the wafer during the plasma etching process are hardly separated from the tissue.

[0004]

2. Description of the Related Art However, as the degree of integration of semiconductors has increased, strict material requirements have also been imposed on electrode materials for plasma etching, and it has been strictly required to reduce the level of particles attached to the wafer surface and the degree of wear. Have been. For this reason, many attempts to improve the material properties of glassy carbon electrodes for plasma etching have been proposed.

For example, in order to improve the material properties such as purity, porosity, pore diameter, and crystal structure, crystallites having a porosity of 0.0002 to 0.0020% are not detected by X-ray diffraction. A carbon member for a plasma device comprising a glassy carbon material having an impurity content of 5 ppm or less (Japanese Patent Laid-Open No. 3-33007), a maximum pore diameter of 1 μm or less, an average pore diameter of 0.7 μm or less, and a porosity of 1% or less. An electrode plate for plasma etching made of high-purity glassy carbon having the following structural characteristics (Japanese Patent Laid-Open No. 3-119723), a plate made of high-purity glassy carbon and having a thickness of 2 mm or more, having a surface and internal structure Electrode plate for plasma etching having substantially no grain boundaries and having a maximum pore diameter of 1 μm or less (JP-A-3-285086), having a purity characteristic of 5 ppm or less in total ash, 2 ppm or less in metal impurities, and 3 ppm in total sulfur. ppm or less, the crystal characteristic lattice spacing (002) 0.375Nm or less, crystallite (002)
Has a size of 1.3 nm or more and material properties of specific gravity 1.5
0 or more, and an electrode plate for plasma etching made of glassy carbon having a bending strength of 1100 kg / cm ² or more
JP-A-320955), an electrode plate for plasma etching made of glassy carbon having a crystallite having a lattice constant C ₀ of 6.990 Å or less (JP-A-6-128761).
Surface smoothness of the part consumed by plasma is Rmax6μm
The following electrode plates for plasma etching made of glassy carbon (JP-A-6-128762) have been proposed.

Further, as a material for specifying a raw material resin for producing glassy carbon, an electrode plate for plasma etching comprising a glassy carbon material produced from phenol resin and polycarbodiimide resin (Japanese Patent Laid-Open No. 5-347276). Also, an electrode plate for plasma etching made of a glassy carbon material manufactured using a polycarbodiimide resin as a raw material (Japanese Patent Laid-Open No. 5-347278) has been proposed.

[0007]

One of the important technical elements in the plasma etching process is an etching rate (speed), and it is necessary to ensure the uniformity of the etching rate in order to increase the processing accuracy. The uniformization of the etching rate is remarkably governed by the temperature of the reaction part, especially the temperature distribution on the surface of the electrode plate. If the surface temperature fluctuates, a uniform and stable etching rate cannot be obtained. Therefore, conventionally, in order to keep the temperature of the electrode plate generating heat by plasma irradiation uniform, a metal cooling plate is used in a stacked state in which a metal cooling plate is closely attached to the back surface of the electrode plate.

[0008] Furthermore, with the increase in the degree of integration of semiconductor devices, circuit patterns have become increasingly finer, and since the wafer size has become more than 8 inches, and even more than 12 inches, the uniformity of the etching rate has been required for large wafers. It is considered to be an important technical issue in performing high-precision etching.

In recent years, as the degree of integration of semiconductor devices has increased, it has been required to further reduce fine particles detached from the tissue, thereby suppressing the consumption of the electrode plate surface during plasma etching. Is becoming increasingly important. Although the glassy carbon material has excellent chemical stability, it gradually depletes from the surface of the electrode plate due to the reaction with the plasma gas during etching. The board has been replaced. Therefore, to develop an electrode plate for plasma etching that can be used stably for a long time with less consumption of the electrode plate surface is necessary to reduce detachment of fine particles that cause wafer contamination. It is extremely important from the viewpoint of economy.

The present inventors have conducted various studies on the above-mentioned problems, that is, the material properties of the glassy carbon material in order to make the etching rate uniform and suppress the consumption of the electrode plate surface. It is important to keep the temperature distribution on the surface of the electrode plate uniform in order to make the electrode plate uniform, the thermal conductivity of the glassy carbon material constituting the electrode plate is above a specified value, and the thickness of the electrode plate is Is more than a certain value, the temperature distribution on the electrode plate surface is equalized,
It has been found that processing can always be performed with an excellent etching rate.

When the bulk density of the glassy carbon material is above a specific value, the temperature rise on the surface of the electrode plate can be suppressed, and the shape of the glassy carbon plate can be reduced by the reaction area of the electrode plate surface where plasma etching is performed. It was clarified that the temperature rise on the surface of the electrode plate can be effectively suppressed by setting the thickness relatively to the thickness.

The present invention has been completed based on the above findings, and an object of the present invention is to equalize the temperature distribution on the electrode plate surface and to suppress the temperature rise on the electrode plate surface. A plasma made of a glassy carbon plate capable of improving the uniformity of the etching rate and reducing the consumption rate, and performing a stable etching process for a long period even for a large wafer exceeding 8 inches. It is to provide an electrode plate for etching.

[0013]

According to a first aspect of the present invention, there is provided an electrode plate for plasma etching according to the present invention, wherein a phenol resin precondensate obtained by a condensation reaction using purified phenol and formalin as raw materials. A resin composition formed by mixing furan or a derivative compound thereof, forming the resin composition, heating and curing, and then carbonizing and calcining a glassy carbon plate produced by firing. The temperature of the carbon plate is 300K
Are characterized by having a thermal conductivity of 5 W / m · K or more and a thickness of 4.5 mm or more. In the electrode plate for plasma etching according to the second aspect, the bulk density of the glassy carbon is 1.53 g.
/ Cm ³ to have the above characteristics, the plasma etching electrode plate according to claim 3, in claim 1 or 2, characterized in that the diameter / thickness ratio comprises a 65 following shape characteristics.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The electrode plate for plasma etching of the present invention has a uniform structure obtained by firing and carbonizing a thermosetting resin, and is premised on a disk-shaped glassy carbon plate. It is preferable that the flat plate is made of a high-purity material having a total ash content of 5 ppm or less, a metal impurity of 2 ppm or less, and a total sulfur content of 30 ppm or less and having as high a surface smoothness as possible.

One of the features of the present invention is that the above-mentioned glassy carbon plate has a characteristic that the thermal conductivity at a temperature of 300 K is 5 W / m · K or more. A glassy carbon plate having a large thermal conductivity has good thermal conductivity, and thus contributes to reducing the temperature fluctuation of the electrode plate and equalizing the surface temperature distribution. In other words, when the thermal conductivity at a temperature of 300 K has a characteristic of 5 W / m · K or more, the heat conduction is performed smoothly, and it effectively functions to maintain the temperature distribution of the electrode plate uniformly. However, the thermal conductivity at a temperature of 300 K is 5
With glassy carbon plates of less than W / m · K, the temperature of the electrode plate tends to change due to the heat generated by plasma etching and the temperature distribution is difficult to be uniform. Become. In addition, the temperature distribution of the electrode plate reduces the adhesiveness due to the stress strain applied to the cooling plate, causing a slight gap, further expanding the temperature distribution of the electrode plate, and changing the surface temperature to reduce the uniformity of the etching rate. .

In addition to these characteristics, the requirement of the present invention to select a glassy carbon plate having a thickness of 4.5 mm or more as an electrode plate means an electrode plate made of a thick glassy carbon plate. In this way, the thick glassy carbon plate has a large heat capacity and effectively suppresses the fluctuation of the surface temperature distribution even when the electrode plate has a slight warp and the adhesion to the cooling plate is impaired. Thus, it is possible to obtain practically sufficient uniformity of the etching rate. However, in the case of an electrode plate made of a glassy carbon plate having a thickness of less than 4.5 mm, the above-mentioned function is not exhibited, and the uniformity of the etching rate is reduced. A thick electrode plate is excellent for handling large-sized wafers and has a secondary effect such as prolonging the life of the electrode against consumption. However, if the thickness is less than 4.5 mm, it is devised during manufacturing. It is difficult to obtain a glass-like carbon plate without warpage as an electrode plate having a large diameter unless stiffening is performed. The thickness that can be stably manufactured as a glassy carbon plate having the texture required for an electrode plate for plasma etching is about 8 mm in the state of the art.

Another feature of the present invention is that the glassy carbon plate has a bulk density of 1.53 g / cm ³ or more. The bulk density of 1.53 g / cm ³ or more is higher than that of a normal glassy carbon material, and is characterized by the fact that the material structure is dense. As a result, the heat capacity is increased, and the heat generated during plasma etching is increased. This effectively functions to suppress a rise in the temperature of the electrode plate. Therefore, the temperature rise on the electrode plate surface due to the plasma reaction is reduced, and the consumption rate is reduced. However, with a glassy carbon material having a bulk density of less than 1.53 g / cm ³ , the temperature of the electrode plate surface increases due to insufficient suppression of the temperature rise of the electrode plate, and the consumption reaction proceeds more rapidly. Become.

Further, another feature of the present invention is that the glassy carbon plate has a shape characteristic having a diameter / thickness ratio of 65 or less. This shape characteristic is characterized in that the thickness is relatively large with respect to the area of the electrode plate surface involved in the plasma reaction, and the heat capacity with respect to the calorific value per unit surface area can be relatively increased. The temperature rise on the electrode plate surface is effectively suppressed, and the consumption rate can be kept low. In addition, even if the electrode plate is slightly warped due to its relatively large thickness, heat transfer with the cooling plate is performed smoothly, and fluctuations in temperature distribution and temperature rise on the surface of the electrode plate are effectively suppressed. be able to. However, if the diameter / thickness ratio exceeds 65, it is not enough to suppress the temperature rise on the surface of the electrode plate, so that the consumption rate cannot be kept low.

As described above, the present invention uses a glassy carbon plate having a thermal conductivity of not less than 5 W / m · K at a temperature of 300 K and a thickness of not less than 4.5 mm for plasma etching. By configuring the electrode plate, the etching rate can be made uniform and the consumption rate can be reduced. Further, the bulk density of the glassy carbon plate is 1.53.
g / cm ³ or more, and having a shape characteristic with a diameter / thickness ratio of 65 or less, these characteristics act synergistically to provide uniform etching rate and especially It is possible to further reduce the consumption speed.

The glassy carbon plate having the above-mentioned properties can be prepared, for example, by mixing furan or a derivative compound thereof with a phenol resin having a molecular weight of 100 or more and a gelling time of 5 to 60 minutes, having a viscosity of 1 to 100 poise and a resin content of 50 weight. % Or more of the resin composition, molded and cured, and then calcined and carbonized in a non-oxidizing atmosphere. Normally, glassy carbon sheets tend to have a large difference in structure, such as the degree of development of carbon crystals between the inside and the outside, and denseness. In particular, this tendency becomes more pronounced as the thickness increases, and cracks occur during the heat treatment process. However, in the above-described manufacturing process, the design of the raw material system, the rate of temperature rise for curing the resin composition, the final curing temperature, uniform heating during calcined carbonization, the rate of temperature rise, the pressure conditions, and the final firing temperature By strictly controlling such factors, it becomes possible to produce a glassy carbon plate satisfying the physical requirements of the present invention. In addition, as a raw material resin, including a conventionally used phenolic resin, furan resin, polyimide resin, polycarbodiimide resin, etc. as a starting material, by strictly controlling the conditions of the manufacturing process, Thus, a glassy carbon material satisfying the characteristic requirements of the present invention can be obtained.

An example of a specific manufacturing process will be described below. First, furan or a derivative compound thereof is mixed with a phenol resin initial condensate obtained by a condensation reaction using purified phenol and formalin as raw materials and having a molecular weight of 100 or more and a gelation time of 5 to 60 minutes to obtain a carbonization yield of 65%. ~ 75
% Of the two-component resin composition. In this case, as the furan derivative compound to be used, one having a compatibility with a phenol resin such as furfuryl alcohol, furfural, methyl furancarboxylate, or a mixture of two or more thereof is used. The mixing ratio of the furan-based component to the phenolic resin is appropriately set according to the properties of the resin, and is adjusted to a property having a viscosity of 1 to 100 poise and a resin content of 50% or more.

Next, the resin composition is molded into a disk by cast molding, centrifugal molding, injection molding, or the like, and is heated and cured in the atmosphere. If there is a difference in the internal structure of the cured molded body at this stage, the difference in the degree of development of the carbon crystal also appears in the finally obtained glassy carbon plate, so the curing conditions are strictly controlled. There is a need to. In general, the curing of a thermosetting resin is an exothermic reaction, and as the thickness increases, the internal heat storage increases. Therefore, the inside of the heat storage resin having a higher heat storage degree is more easily cured than the surface layer. In order to avoid such non-uniformity of curing, the rate of temperature rise during heating and curing is 10 ° C./hr or less, preferably 5 ° C./hr or less, more preferably 2 ° C./hr.
Adjust to the following. Next, the heating temperature is increased to a temperature at which the curing reaction is completed, and the composition is held for a sufficient time to be completely cured. The curing temperature varies depending on the composition of the resin, the type of the curing agent, the composition, and the like, but is usually kept in a temperature range of 140 to 200 ° C. When the final curing temperature is low, holding for a long time is necessary. Even when the curing temperature is high, it is preferable to keep the temperature for 3 hours or more.

The cured resin article is packed in a heating furnace maintained in a non-oxidizing atmosphere, and calcined at a temperature of 800 ° C. or more to be converted into a glassy carbon plate. Since the cured resin has a low thermal conductivity, if the thickness is increased, the decomposition and carbonization reaction of the internal structure is delayed in the vicinity of the surface layer during the firing and carbonization. For this reason, as a result of carbonization progressing in a state where the inside is under tension with the preceding of carbonization in the vicinity of the surface layer, a difference in thermal conductivity between the surface layer and the interior is likely to occur. In order to alleviate such a phenomenon, the temperature rise rate of the calcined carbonization is set to 4 ° C./hr or less, and the inner and outer layers are carbonized at a uniform rate by gradually increasing the temperature. Furthermore, the resin molded body is packed in a graphite crucible in a pressurized state sandwiched between graphite plates and set in a heating furnace, and the calcined carbonization temperature is adjusted within a range of 1000 to 2500 ° C. while maintaining the inside of the furnace under pressurized conditions. By doing so, a glassy carbon plate having different physical properties such as thermal conductivity and bulk density is manufactured.

In addition, during the heating process during the firing carbonization, the temperature may be maintained at each stage of a temperature range in which carbonization is severe, a temperature range in which gas is intense, and a temperature range in which carbonization is completed and a structural change occurs. This is an effective means for reducing the difference between the inner and outer structures. Specifically, 300-400 ° C, 400-
Each of the temperature steps of 500 ° C. and 500 to 600 ° C. is held for 5 hours or more.

After the calcination and carbonization, the glassy carbon plate is highly purified by performing a high temperature treatment at 1400 ° C. or more while introducing a halogen gas such as chlorine into the furnace as necessary. The gas flow through holes provided in the electrode plate may be drilled in the cured resin plate at the resin molding stage in advance in view of the dimensional shrinkage ratio at the time of carbonization, or may be formed in the fired glassy carbon plate by electric discharge machining. Or one of two methods.

[0026]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples, but the embodiments of the present invention are not limited to these examples.

Examples 1 to 13 and Comparative Examples 1 to 6 (1) Production of electrode plate for plasma etching Phenol and formalin purified by distillation under reduced pressure were subjected to a condensation reaction in the presence of ammonia, and the molecular weight and gel shown in Table 1 were obtained. A phenolic resin precondensate of the aging time was prepared. 30 parts by weight of furfuryl alcohol was added to and mixed with 100 parts by weight of this phenol resin, and the viscosity was 40 poise.
A resin composition having a resin content of 55% was obtained. The resin composition was poured into a polyethylene vat, placed in a vacuum desiccator, subjected to a defoaming treatment under a reduced pressure of 10 Torr, transferred to an electric oven, and heated to 200 ° C. at a rate of 4 ° C./hr. A hardening treatment was performed under the condition of keeping the temperature for 5 hours to produce disc-shaped molded articles having different diameters and thicknesses.

Next, both side surfaces of each disk-shaped molded product were
It was sandwiched between graphite plates of 0 mm (G347, manufactured by Tokai Carbon Co., Ltd.), placed in a graphite crucible, packed in an electric furnace maintained in an argon atmosphere, and subjected to a calcination carbonization treatment. At this time, the pressurized state of the electric furnace with argon gas was changed,
Slowly raise the temperature at a rate of 1 to 4 ° C./hr and
The calcined carbonization conditions for holding at each of the temperature stages of 50 ° C., 450 ° C., and 550 ° C. for 5 hours and finally treating at a predetermined temperature were set. Furthermore, a high purity treatment was performed at the same temperature as the final treatment temperature during calcining and carbonization while flowing chlorine gas through the furnace to produce glassy carbon plates having smooth surfaces with different diameters and thicknesses. In the center of the obtained glassy carbon plate, through holes having a diameter of 0.6 mm were formed at equal intervals of 2 mm by electric discharge machining to obtain an electrode plate for plasma etching.

The physical properties of each of the obtained glassy carbon plates were
The results are shown in Table 2. Thermal conductivity is JIS R161 among physical properties
It was measured according to 1-191. The specific heat capacity used was high-purity α-alumina as a standard sample, blackened aluminum was used as a light-receiving plate, and the heat diffusivity was high-purity copper as a standard sample. The bulk density is JIS Z8807-1.
Archimedes method according to 987 (method of weighing in liquid)
Was measured by

[0030]

[Table 1]

[0031]

[Table 2]

(2) Evaluation of Performance of Electrode Plate Each electrode plate made of a glassy carbon plate having the physical properties shown in Table 2 was set in a plasma etching apparatus, and the processing time was 1 hour.
The uniformity of the etching rate of the silicon wafer and the consumption of the electrode plate after the lapse of 00 hours and 200 hours were measured, and the results are shown in Table 3. In addition, the etching process is performed using a reaction gas; CF ₄ , a carrier gas;
Gas pressure in reaction chamber; 1 Torr, power supply frequency; 1
The test was performed on an 8-inch silicon wafer oxide film under the condition of 3.56 MHz. The amount of electrode consumption was calculated by the following equation from the thickness reduction of the electrode plate after processing, and the uniformity of the etching rate (E / R uniformity) was calculated from the nine etching rates including the center of the wafer.

[0033]

[Table 3]

From the results in Tables 2 and 3, the uniformity of the etching rate and the amount of consumption of the electrode plate surface after 200 hours are shown in FIGS. The electrode plate for plasma etching made of glassy carbon according to the embodiment, which has a thermal conductivity of 5 W / m · K or more at a temperature of 300 K and a thickness of 4.5 mm or more, is provided by the present invention. It can be seen that the uniformity of the etching rate is excellent even when the etching process is performed for a long time, and the amount of consumption of the electrode plate surface is small, as compared with the electrode plate of the comparative example which does not satisfy any one of the characteristic requirements. Furthermore, in the case where the glassy carbon plate also has a characteristic of a bulk density of 1.53 g / cm ³ or more and / or a shape characteristic of a diameter / thickness ratio of 65 or less in the examples, FIGS. As shown, in addition to the uniformity of the etching rate, it is recognized that more excellent performance is exhibited, particularly under a reduced consumption rate.

[0035]

As described above, according to the present invention, by selecting a glassy carbon plate having a thermal conductivity of a specific value or more and a thickness of a certain value or more, a large semiconductor wafer can be uniformly etched. Thus, it is possible to provide an excellent electrode plate for plasma etching, in which the surface of the electrode plate is less consumed and has a long service life. Furthermore,
By selecting and using a glassy carbon plate having a bulk density of a specific value or more and a diameter / thickness ratio of a certain value or less, it becomes possible to further improve the etching rate and the consumption rate of the electrode plate surface. Therefore, stable etching is ensured over a long period of time, and the durable life of the electrode plate can be greatly improved. This greatly contributes to the industry.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between thermal conductivity and uniformity of an etching rate.

FIG. 2 is a graph showing a relationship between a thermal conductivity and a consumption amount of an electrode plate surface.

FIG. 3 is a graph showing a relationship between a bulk density and a consumption amount of an electrode plate surface.

FIG. 4 is a graph showing a relationship between a diameter / thickness ratio and a consumption amount of an electrode plate surface.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-260078 (JP, A) JP-A-4-50108 (JP, A) JP-A-5-129241 (JP, A) JP-A-5-129241 347276 (JP, A) JP-A-7-292484 (JP, A) JP-A-5-48333 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065 C04B 35 / 52 C23F 4/00 C01B 31/02 101

Claims (3)

(57) [Claims] 1. A resin composition is formed by mixing furan or a derivative compound thereof with a phenol resin precondensate obtained by performing a condensation reaction using purified phenol and formalin as raw materials, and forming the resin composition. After heating and curing, it is made of a glassy carbon plate manufactured by carbonization and firing.
An electrode plate for plasma etching, having a characteristic that the thermal conductivity at 0K is 5 W / m · K or more and the thickness is 4.5 mm or more. 2. A glassy carbon plate having a bulk density of 1.5
2. The electrode plate for plasma etching according to claim 1, wherein the electrode plate has a characteristic of 3 g / cm ³ or more. 3. A glassy carbon plate having a diameter / thickness ratio of 6
3. The electrode plate for plasma etching according to claim 1, wherein the electrode plate has a shape characteristic of 5 or less.